Particles in the transformer oil adversely affect the dielectric strength of the insulating oil. Depending on type, size and quantity of particles (metallic, water etc.), a flash-over could be generated, which can be hazardous…

Automatic Particle Counters are used for an array of specific specialized applications, including quality control of liquid filled power transformers. Due to the high amount of transferred voltage, transformers are rapidly heated up, and thus need to be adequately cooled. Power transformers are usually cooled with oil (e.g., mineral oil or silicone transformer liquid). The insulating oil does not only serve as coolant, but it also insulates empty spaces between conductive materials. Particles in the oil adversely affect the dielectric strength of the insulating oil. Depending on type, size and quantity of particles (metallic, water etc.), a flash-over could be generated, which can be hazardous. The oil itself turns into an electrical conductor and hence loses its insulating function.

Before a transformer is put into operation, the insulating oil needs to be monitored with a particle counter. In the case of an alarmingly high particle concentration, the oil must be treated or replaced in order to decrease the possibility of a flash-over. Water droplets in the oil (for instance) can be eliminated through prior drying. Solid particles are removed through filtration. While the oil is being processed or while the transformer is being filled with oil for the first time, the particle counter monitors the oil cleanliness. As soon as pre-defined oil cleanliness is achieved, the flushing process is stopped automatically. The oil cycle of a filled transformer is hermetically sealed, so contaminants from the external environment are unable to enter the system. Due to case vibrations and mechanical switches, however, the particle number in the insulating oil rises during operation. It is therefore imperative to monitor the insulating oil regularly during operation. If too many particles are counted, filtration or exchange of the insulating oil will ensure trouble-free and safe operation.

The analysing methods for particle counting of insulating liquids are standardised in the IEC 60970 and the ASTM D6786. Both standards require the calibration of Automatic Particle Counters according to ISO 11171.

Founded in 1992, PAMAS develops, liquid particle counters to measure particulate contamination in liquids. The highly sophisticated optical sensors are manufactured at the company’s plant in Germany. Due to its own R&D, PAMAS is the market leader for high-quality liquid particle counting systems. Manufacturers and operators of transformer systems acknowledge and appreciate PAMAS (www.pamas.de) particle counters due to their reliability, their measuring accuracy and their multiple application profiles.

In India, Pamas has a full-fledged application and service lab in Bangalore, and the company operates through a network of distributors throughout the country.